Mercury switch



Jan. 3, 1939. W. MURAI'D 2,142,326

MERCURY SWITCH Filed Jan. 27, 1931 2 Sheets-Sheet 2 ATTORNEYS.

Patented Jan. 3, 1939 RE'IS'S UE c DEC 241940 MERCURY SWITCH WalterMurad, Burlingame, Calif., assignor of i one-half to Charles S. Evans,San Francisco,

Calif.

Application January 27, 1931, Serial No. 511,537

Claims.

the neighborhood of radio receiving sets or other electrically operatedsound reproducing apparatus, since the surges set up create disturbancesin the apparatus. In order to prevent arcing at the contacts, switchesheretofore employed have been designed to make and break the circuitrapidly, a spring biased snap action being usually provided foreffecting this result. The noise attendant Aupon the operation of suchswitches is not pleasant and frequently, as when the switches areemployed in places where silence is desired, this also is a source ofannoyance.

It is a general object of my invention to provide a switch which iseiiicient and reliable in operation.

Another object is to devise a switch in which means is provided foropening and closing a circuit relatively gradually, thereby eliminatingelectrical surges.

Another object is to devise a switch in which means is provided forprecluding arcing at the contacts and which is, nevertheless, silent inoperation.

Another object is to provide a switch utilizing mercury or the like forbreaking the circuit and in which the electrical connection between thecontacts is made and broken in the body of mer- Cary.

Still another object is to provide a switch which is simple andeconomical in'construction.

A further object is to devise a novel method of manufacturing the switchof the present invention.

These andv other objects and advantages are attained in the embodimentsof my invention i1- llustrated in the accompanying drawings, in

which:

Fig. 1 is a cross sectional view taken on a vertical plane, of oneembodiment of my invention, illustrating a switch of the wall type inopen position.

Fig. 2 is a similar view showing the switch illustrated in Fig. 1 inclosed position.

Fig. 3 is a front elevation of the switch with the cover removed to showthe construction.

Fig. 4 is a cross sectional view taken on line 4 4 of Fig. 3.

Fig. 5 is a view showing certain details of the device.

Fig. 6 isa cross sectional view of a modification in which the body ofmercury employed in the switch remains relatively stationary and thecontacts are movable into and out of engagement with the mercury. Inthis figure one manner is illustrated in which a plurality oi switchesof the type disclosed can be mounted within a single housing.

Fig. '7 is a cross sectional view taken on line 'lf-l of Fig. 6.

Fig. 8 is a cross sectional View taken on line 8-8 of Fig. 7.

Fig. 9 is a perspective view of a detail.

In its preferred form the switch of my invention comprises a body ofmercury which is adapted to be caused to iiow into and out of engagementwith one or more contacts of the switch to eiect opening and closing ofthe circuit controlled by the switch. Preferably, means is provided formaking and breaking the circuit in the body of mercury, thereby causingany arcing which does take place to occur between two points in themercury. Also, means can be provided for causing the circuit to be madeand broken gradually thereby eliminating electrical surges in thecircuit.

Referring now to the drawings and first to Figs. 1 to 5 thereof, I haveshown a switch of the wall type having a housing I6 formed of suitableinsulating material, such as porcelain, a phenol condensate product, orthe like. A pair of brackets I1 and I8 can be provided each having oneor more apertures therein for the reception of screws I9 for securingthe housing to a wall or other suitable support.

A pair of conducting brackets 2| and 22, each having an upstanding leg23 and 24 preferably extending substantially perpendicular to the baseof housing i6, are secured in any suitable manner to the housing I6, asby means of screws 26. The brackets 2l and 22 are provided with bindingposts 21 for connecting the switch in the electrical circuit which is tobe controlled by the switch.

In the embodiment illustrated in Figs. 1 to 5, the actuating member ofthe switch comprises a tumbler 28, mounted for rocking movement about anaxis extending between the upper portions of legs 23 and 24. The tumbler28 is preferably made hollow and is provided with a pair of conductingplugs 3| and 32 extending from the 1nterior of the tumbler to theexterior thereof. The inner faces 33 and 34 of the plugs 3| and 32constitute the contacts of the switch and in addition the plugs 3| and32 can serve as trunnions for mounting the tumbler for rocking movement.For this purpose each of the plugs 3| and 32 is bevelled at its outerend, as at 36 and 3l, and is journalled in a bearing formed in each ofthe legs 23 and 24. In the embodiment illustrated, the legs 23 and 24have depressions 38 and 39 stamped or otherwise formed therein intowhich the bevelled ends 36 and 3l, respectively, can extend. It is to beunderstood that the bearings need not be in the form of depressions andthat if desired, any other suitable arrangement can be employed forjournalling the tumbler for rocking movement. I have found, however,that the type of bearing shown gives good results, since wear isautomatically taken up and good electrical contact between the plugs andthe supporting brackets is provided at all times.

The tumbler 28 is preferably composed of moldable insulating material,such as a phenol condensate product, and the hollow compartment formedtherein is shown as being divided into two parts 4| and 42 by apartitioning wall 43 extending longitudinally through the handle of thetumbler. A quantity of mercury 44 is disposed within the compartment andwhen the switch is mounted in operative position, the mercury can becaused to ow from one end of the tumbler to the other upon rockingmovement thereof. For example, when the tumbler is rocked to theposition illustrated in Fig. 1, the mercury nows to the outer end of thehandle and when it is rocked to the position shown in Fig. 2, themercury llows to the inner end.

When the tumbler is in the position shown in Fig. 2, the mercury takesthe form of a single globule since the partitioning wall in the handlepreferably does not extend as far as the inner end wall of thecompartment. When the tumbler is tilted to the position shown in Fig. 1,however, the mercury is divided into two parts by the partitioning wall,one part flowing into compartment 4| and the other part flowing intocompartment 42. As shown in Figs. 2 and 4, when the mercury is at theinner end of the tumbler, it engages both contacts 33 and 34 therebyserving to complete an electrical circuit in which these contacts may beincluded. It will also be noticed that when the tumbler is rocked to theposition shown in Fig. 1, the mercury Iiows away from the contactsthereby breaking the circuit.

Preferably, the inner edge of the partitioning wall 43 is disposedbetween the contacts 33 and 34, as shown i n Figs. 2 and 4, so that asthe mercury recedes from the inner end of the tumbler it is divided intotwo portions before it has left either one of the contacts 33 and 34. Ina similar manner, when the mercury is flowing toward the contacts, theglobule of mercury 1n compartment 4| makes engagement with contact 33and the globule of mercury in compartment 42 engages contact 34 beforethe two globules of mercury have reached the position where they flowtogether to form a single globule. By providing means of this characterfor parting the mercury upon opening the switch before the mercury hasleft either contact and for causing the mercury to make engagement withboth of the contacts 33 and 34 before it is permitted to ow together onthe closing of the switch, the circuit will be made and broken withinthe body of the mercury. Thus, no arcing can possibly occur at thesurfaces of the contacts 33 and 34 and any arcing which may take placemust occur in the body of the mercury.

The inner edge 45 of the partitioning wall 43 is preferably bevelled orsharpened and is in the form of a knife edge so that at the instant themercury is separated'or reunited, as the case may be, the change iseffected smoothly and gradually. As the mercury recedes from thecontacts 33 and 34 upon tilting of the tumbler, the effective crosssection through the body of mercury decreases gradually, therebyincreasing the resistance between the contacts. The rate of change inthe cross section of the mercury during this movement can be accuratelycontrolled by suitably shaping the knife edge 45 and I have shown acurved portion 46 on the knife edge for this purpose. Thus, the currentin the circuit is gradually reduced to a minimum value before thecircuit is finally broken. At the instant of final break, the currenthas reached its minimum value and any arcing which may occur willnecessarily be of little consequence.

At the instant of separation, the surface tension of the mercury causesthe separated globules to withdraw violently from one another, therebyabruptly breaking the circuit. Thus, not only is the arcing which mayoccur of small magnitude, but it is also of extremely short duration.Experiments have shown that the amount of arcing is negligible inswitches constructed in accordance with this invention and that thequality of radio reception, for example, is not disturbed in theslightest by the operation of such switches, even when employed underthe most adverse conditions.

Since the elimination of arcing in the present switch is not dependentupon the rapidity of movement of the actuating member, no provision needbe made for biasing the member toward open and closed positions. Thestructure can be materially simplified, therefore, by omitting theusually complicated mechanism ordinarily employed for this purpose.Consequently, the switch is absolutely silent and free of all mechanical noises.

Suitable means can be provided, if desired, for retaining the switch ineither one orboth of its operating positions. Thus, in Fig. 5 I haveshown a at surface 48 formed on the bevelled end of trunnion 3| which isadapted to cooperate with a complementary fiat surface 49 in the bearing38 for retaining the switch in one of its actuated positions. Thisexpedient can also be employed in the other trunnion 32 to reinforce theholding eiect or, if desired, one of the trunnions can be provided witha surface which serves to hold the switch on while the other can have asurface to hold the switch oif.

For precluding oxidation or other deterioration of the mercury, thecompartment or bore within the tumbler 28 can be filled with some inertgas or, if desired, it can be partially evacuated. For ordinaryconditions I have found that a rareed atmosphere of air gives very goodresults.

In manufacturing the tumbler 28, I prefer to employ a moldableinsulating material, such as a phenol condensate product, which can bemolded to the desired shape directly about the trunnions 3| and 32 andwith the partitioning wall 43 formed integrally within the handle of thetumbler. The open end of the tumbler can have secured therein, in anysuitable mannera. plug 5I of insulating material having an opening 52for evacuating the compartment after the mercury has been deposited.After the chamber has been evacuated sufficiently, the opening 52 can besealed with sealing wax 53 or any other suitable non-conducting sealingmaterial.

The preferred method of manufacture, how-'- ever, is to heat the tumblerand the mercury which is placed therein, thereby expanding the tumblerand heating the air in the compartment. While the tumbler is still inheated condition, an unheated solid plug 54, shown in Fig. 4, can beforcibly inserted in theopen end of the tumbler. Upon cooling, thetumbler will contract about the plug, thereby holding it securely inplace and the contraction ofthe air upon cooling will produce thedesired rareed atmosphere. Under some circumstances, I have found thatthe presence of a small amount of carbon in the mercury, in theneighborhood of about one per cent (1%) has a beneiicial influence.

The legs 23 and 24 are formed of metal having good electricalconductivity and preferably having sufticient resiliency to support thetumbler 28 without further aid. Brass or hard drawn copper aresatisfactory, but it is to be understood that practically any othermetal can ben employed. In view of the inherent ruggedness of the switchand the entire absence of. breakable parts, the possibility of failureis extremely remote. However, if for any reason it is desired to replacethe tumbler 28, the construction permits easy withdrawal thereof and anew tumbler can be readily snapped into place, thereby reconditioningthe switch Without disturbing any wiring in the circuit.

yThe usual wall plate 56 can be disposed over the front side of theswitch and secured thereto, as by means of screws 51. The tumbler 28 canhave molded or otherwise formed thereon, suitable legends 58 to indicatethe open or closed condition of the switch.

In the embodiment illustrated in Figs. 1 to 5 and which has beendescribed above, it will be noticed that the mercury in flowing to andfrom the contacts changes its position relative to the axis of rotationof the tumbler 28. In Figs. 6 to- 9, I have illustrated a modificationlin which the mercury remains substantially stationary relative to theaxis of rotation of the actuating member while the switch contacts canbe moved into and out of engagement with the mercury. The generalprinciple of operation, however, is substantially the same as in theembodiment heretofore described.

Referring now to Figs. 6 to 8, I have shown a switch having a base 6I towhich a pair of conducting brackets 62 and 63 are secured, as by meansof screws 64. The movable member 66 of the switch can be of a generalcylindrical shape and can have a compartment 61 therein. The member 66is provided with trunnions 69 and 1| and is journalled'for rockingmovement in bearings 68 formed in or carried by the brackets 62 and 63.y

The trunnions 69 and 1| arepreferably made of conducting material andextend from the exterior of the member 66 into the compartment 61.Electrically connected to the trunnions are conducting strips 12 and 13which can be disposed against opposite sides of the chamber 61. Thestrips 12 and 13 extend to a point near the peripheral wall of thechamber 61 and rotate with the member 66 as it is rocked from onepositionA to another.

A quantity of mercury 14 is disposed within the compartment 61 and whenthe conducting strips 12 and 13 are rocked to the position shown in Fig.7, they are electrically connected together member 66.

For parting the Amercury 14 so that the circuit is made and brokenwithin the body of the mercury, a severing member 16 is provided whichhas formed thereon one or more severing blades 11 and 18. In theembodiment illustrated, two blades are shown, whereby the mercury issevered linto three parts. VThe operation of the blades 11 and 18 issimilar in every respect with the operation of the partitioning member43, heretofore described in connection with the other embodiment.

For rotating member 66 a suitable handle 19 can be provided and ifdesired, suitable stops 8| and 82 can be provided on member 66 which areadapted to cooperate with a fixed stop 83 for limiting the rockingmovement of member 66.

In Fig. 6 I have illustrated one manner in which a plurality of switchesof the type described can be mounted within a single housing 84 forsimultaneous operation. Thus, three, switches 86, 81 and 88 have beenshown linked together, as by means of a bar 89, and are alll operableupon actuation of a single handle 19. When all three switches. areconnected in parallel and to control the same circuit, the resultingswitch is suitable for heavy duty, since the current in the circuitdivides through the three switches. Also, by a similar construction, amultiple switch can be provided merely by shifting the phaserelationship of the actuating members 66 on the diiferent switches sothat each switch operates in succession as the actuating handle 19 ismoved from one of its extreme positions to the other. For example, thephase relationship between the switches can be such that the switch 86closes when the handle is in its vertical position, as shown in Fig. '1,while switch 81 closes when the handle is thirty degrees removed fromthis position and switch 88 closes when the handle is sixty degreesremoved from its original position, and all of the switches can be inopen condition when the handle is in its horizontal position. In thismanner any number of switches can be mounted for simultaneous operationand by suitably connecting the various switches into differentelectrical circuits, a wide variety of useful combinations can beproduced.

While I have shown and described certain preferred embodiments of myinvention, I do not wish to be limited thereto, since the invention asdefined in the appended claims can be embodied in a plurality of otherforms.

I claim: i

1. In an electric switch, a housing having a recess therein, meansadjacent the front of said housing for mounting said housing on asupport, a wall plate having an aperture therein, means for fasteningsaid plate on'said mounting means, resilient legs in said recess, and atumbler insertible through said aperture and adapted to be gripped bysaid legs.

2. In an electric switch, a housing having a recess therein, a wallplate having an aperture therein adapted to overlie said recess,resilient legs in said recess, a tumbler partially disposed in saidrecess and projecting through said aperture,

and plugs on said tumbler releasably engaging said legs, said tumblerbeing adapted to pass bodily through said aperture when said legs andsaid plugs are released.

3. In an electric switch, a frame providing a recess, a plate having anaperture therein adapted to overlie said recess, a tumbler adapted topass bodily through said aperture and to be partially disposed in saidrecess, plugs on said tumbler, and resilient legs on said frame adaptedreleasably to engage said plugs.

4. In an electric switch, a frame providing a recess, a plate having anaperture therein adapted to overlie said recess, a hollow tumbleradapted to pass bodily through said aperture and to be partiallydisposed in said recess, electrically conducting plugsin said tumbler,mercury partially lling said hollow tumbler and adapted to controlelectric .flow through said plugs, and a pair of resilient electricallyconducting legs on said frame and providing releasable pivotal supportsfor said plugs.

5. In an electric switch, a frame, a plate having an aperture thereinadapted to overlie said frame, a hollow tumbler adapted to pass throughsaid aperture and to be partially disposed in said recess, electricallyconducting plugs in said tumbler, mercury partially lling said hollowtumbler and adapted to control electric ow through said plugs, and apair of electrically conducting legs on said frame and providing withsaid plugs a releasable pivotal connection ybetween said frame and saidtumbler.

6. In an electric switch, a housing having a recess therein, a planarwall plate having an aperture therein overlying said recess, a pair ofelectrically conducting legs in said recess, electrical terminals onsaid legs, a hollow tumbler adapted to pass bodily through said apertureand to be partially disposed in said recess, electrically conductingplugs in said tumbler and providing with said legs a releasable pivotalconnection between bridging the contacts, and a fusible plug in the baseof the tumbler and closing said bore.

8. A switch comprising a recessed frame, brackets terminating inbearings and mounted in the recess of said frame, a wall plate ilushwith the Wall and covering said frame, a tumbler having trunnionsjournaled in the bracket bearings and extending in a handle through thewall plate, said tumbler having a longitudinal bore extending betweenthe trunnions into the handle, contacts in the bore electricallyconnected with said trunnions, a body of mercury in the tumbler forbridging the contacts, and a fusible plug in the tumbler and closingsaid bore.

9. A switch comprising resilient brackets terminating in bearings, ahollow tumbler, trunnions on the tumbler journaled in the bracketbearings, contacts in the tumbler connected with said trunnions, a bodyof mercury in the tumbler for bridging the contacts, the bearingsurfaces between the trunnions and brackets being tapered so thatpulling on the tumbler causes the brackets to spring outwardly torelease the tumbler.

10. A mercury switch comprising a wall plate, a tumbler having a baseportion positioned behind the Wall plate and having an elongated portionprojecting through the plate to provide a handle, said tumbler having abore through its base to provide a mercury chamber, contacts in thebase, a body of mercury in the tumbler for bridging the contacts, and afusible plug in the base of the tumbler and closing said bore.

WALTER MURAD.

